chore(llmobs): assert using span events instead of mocks

[Yun-Kim]

Follow up of #11781 to further clean up LLMObs tests, specifically replacing potentially flaky LLMObs span writer mocks and assertions with the test LLMObsSpanWriter dummy class. Also clean up the tests/llmobs/conftest.py file which previously contained a ton of rarely used and sometimes redundant fixtures.

Checklist

• PR author has checked that all the criteria below are met
• The PR description includes an overview of the change
• The PR description articulates the motivation for the change
• The change includes tests OR the PR description describes a testing strategy
• The PR description notes risks associated with the change, if any
• Newly-added code is easy to change
• The change follows the library release note guidelines
• The change includes or references documentation updates if necessary
• Backport labels are set (if applicable)

Reviewer Checklist

• Reviewer has checked that all the criteria below are met
• Title is accurate
• All changes are related to the pull request's stated goal
• Avoids breaking API changes
• Testing strategy adequately addresses listed risks
• Newly-added code is easy to change
• Release note makes sense to a user of the library
• If necessary, author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
• Backport labels are set in a manner that is consistent with the release branch maintenance policy

[github-actions]

CODEOWNERS have been resolved as:

tests/llmobs/conftest.py                                                @DataDog/ml-observability
tests/llmobs/test_llmobs_decorators.py                                  @DataDog/ml-observability
tests/llmobs/test_llmobs_evaluator_runner.py                            @DataDog/ml-observability
tests/llmobs/test_llmobs_ragas_faithfulness_evaluator.py                @DataDog/ml-observability
tests/llmobs/test_llmobs_service.py                                     @DataDog/ml-observability
tests/llmobs/test_propagation.py                                        @DataDog/ml-observability

[datadog-dd-trace-py-rkomorn]

Datadog Report

Branch report: yunkim/refactor-span-events
Commit report: 01aac1c
Test service: dd-trace-py

✅ 0 Failed, 1468 Passed, 0 Skipped, 25m 23.96s Total duration (12m 0s time saved)

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-01-09 18:58:32

Comparing candidate commit 76340ca in PR branch yunkim/refactor-span-events with baseline commit d676233 in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 394 metrics, 2 unstable metrics.

[ncybul]

Besides the one comment I left, this LGTM. Thanks for the thorough explanation! Also, feel free to ping for a final pass.